1. Field of the Invention
The present invention relates to a large- or medium-sized collapsible (foldable, spreadable) structure for use in outer space for constructing space colonies, solar power satellite systems, large antennas, space stations and the like or for use on the ground for constructing portable emergency temporary buildings.
2. Description of the Related Art
The volume and weight of payloads to be carried into outer space by a launch vehicle, such as a rocket or a space shuttle, are subject to restrictions placed by the launching ability of the launch vehicle. Therefore, structures to be used in outer space must be lightweight, collapsible for carrying, capable of being easily assembled in outer space and rigid. Under such circumstances, a collapsible structure is considered to be a promising space structure. The collapsible structure is folded in a small volume for launching and is unfolded in outer space in a desired form.
Such a collapsible structure is disclosed in, for example, JP-B No. 26653/1974. This prior art collapsible structure is folded by folding the members thereof at joints placed in their middle parts and has a complex construction. Particularly, the middle parts of the members most subject to buckling have low rigidity and low strength, so that the rigidity and strength of the collapsible structure as unfolded are not necessarily high enough.
The mechanism of the collapsible structure for used in outer space must be highly reliable to enable the collapsible structure to be surely unfolded automatically or semiautomatically in outer space. The applicant of the present patent application previously proposed a rigid, strong collapsible structure comprising members, which are not folded at their middle parts as shown in FIG. 23 in JP-B No. 94236/1995. This collapsible structure has a first set of horizontal members A, B, C and D connected by joints a, b, c and d in a quadrilateral, a second set of horizontal members I, J, K and L connected by joints e, f, g and h in a quadrilateral, and four vertical members E, F, G and H having lower ends connected to the joints a, b, c and d, respectively, and rising from the joints a, b, c and d perpendicularly to a plane including the horizontal members A, B, C and D. The vertical member G, i.e., one of the vertical members E, F, G and H, is longer than the rest. The upper ends of the vertical members E, F and H, and a part of the vertical member G on the same level as the upper ends of the vertical members E, F and H are connected to the joints e, f, h and g, respectively. The vertical member G is provided with a slide hinge M placed on top of the joint g. A diagonal member N connects the joint a and the slide hinge M.
As the slide hinge M slides away from the joint c along a part of the long vertical member G extending upward from the joint g, the diagonal member N is pulled toward the vertical member G, and the vertical member E connected to the joint a approaches the long vertical member G. Consequently, the horizontal members A, B, C, D, I, J, K and L turn on the corresponding joints and, eventually, the diagonal member N, all the short vertical members E, F and H, and the horizontal members A, B, C, D, I, J, K and L are gathered around the long vertical member G so as to extend along the long vertical member G to collapse the collapsible structure. This procedure is reversed to unfold the folded collapsible structure.
Thus, the component members of the prior art collapsible structure need not be folded at their middle parts and need not be contracted to collapse the collapsible structure, and the unfolded collapsible structure has high rigidity and strength. Although the vertical members and the horizontal members are gathered around the long vertical member and the collapsible structure can be folded in a folded structure having small lateral dimensions, the longitudinal dimensions of the folded structure are not necessarily small.